Full movie description "Highway Patrol Efficiency Secretary":

Trusted secretary Doris Mauldin steals $50,000 from the Colton Valley Farmers' Co-Operative and solicits the assistance of her boyfriend "Dusty" Dunn to transport the cash to a safe hiding place in his crop dusting plane. Her manager and co-workers vouch for her honesty and efficiency, but most of the other possible suspects are painstakingly eliminated. When Dan Mathews notices a white dust handprint on the back of Ms. Mauldin's dress, he deduces that she and Dunn are romantically involved. He utilizes a ruse that compels Ms. Mauldin to expose her involvement by attempting to flee with Dunn in his plane.

Reviews of the Highway Patrol Efficiency Secretary

Yet another first rate Highway Patrol episode, Efficiency Secretary
starts slow and is a bit dull for its first few minutes, then picks up
as head of steam. The criminal here is a woman, and she's pretty much
the gang leader: the catch is that she has no background in crime, is
the girl Friday in the agricultural co-op where she works; and prior to
her theft of several thousand dollars of the money of hard-working
farmers, she was an upstanding citizen.

What made her do it is never explained. As I think on it she's a bit
like insurance man Walter Neff of Double Inemnity, also a highly
trusted employee; and Psycho's Marion Crane, the attractive young woman
who absconds with forty grand from her long time employer. All three
characters are middle to low level business types, a far cry from upper
level management, they're not exactly working stiffs, either. They
steal less from greed as a desire to break free from their humdrum
lives.

The character of Miss Mauldin in Efficiency Secretary is the least
sympathetic of the three. I could never warm up to her. There wasn't
much to like, though her professionalism earned my admiration. She was
clever enough to outfox top cop Dan Mathews early on, but even he
noticed that she was almost too efficient, so disciplined and reliable
to actually raise suspicions. Counter-intuitive types, whether in crime
or business, often forget that they can themselves be "counter
counter-intuited" by others and that no, this doesn't take a rocket
scientist, just a professional cop with a keen eye. The episode
features a good story, decent acting and an interesting villain of the
week whose motive is never explained. Indeed, the subject never comes
up.

This one isn't action packed but it's worth sticking with, as it gets
better as the story moves along.